Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already indicate idempotent, non-readonly, non-destructive, and open-world behavior. The description adds real value on top: idempotency-key mechanics, the human authorization step in Stripe, and the explicit warning that this tool never proves payment or phone activation. There is no contradiction with the annotations.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is concise at five sentences, each earning its place: purpose and resource, required params, idempotency guidance, human authorization flow, and exact follow-up routing. Front-loading the purpose minimizes the cognitive cost for the agent.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a state-changing checkout tool with no output schema, the description does a solid job: it names all required inputs, the owner-authorization step, the follow-up tool, and the caveat about payment proof. A minor gap is that it does not detail what fields the response will contain besides session_id and the link, but the agent has enough to invoke and verify correctly.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 0%, so the description must compensate. It gives meaningful semantics for idempotency_key (durable, retry pattern, new key needed for plan change) and plan_id (current plan from list_plans), but it only name-drops business_id without explaining its meaning or source, leaving a gap for agents.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description states a clear verb and resource: 'Create or resume an owner-bound hosted Stripe checkout for a current plan from list_plans.' It also distinguishes this tool from nearby siblings like get_checkout_status by naming the follow-up tool explicitly, and it clarifies the plan source.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description provides direct usage conditions: use a current plan from list_plans, reuse the idempotency key for retries, and change the key when changing plans. It also explicitly says when not to use this tool for payment proof and routes to get_checkout_status with the returned session_id.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.